This invention relates to an endoscope having signal conductors and also to a jig for processing such signal conductors.
An endoscope of the type connectable to a television system is already known, for example, from Japanese Laid-Open (Kokai) Patent Application Nos. 90544/84, 50546/86, 267715/87 and 21618/88. Such an endoscope, like other types of endoscopes, comprises a hollow body, a flexible hollow insertion portion extending from the front end of the hollow body, a flexible hollow bending portion extending from the distal end of the insertion portion, and a rigid portion provided at the distal end of the bending portion. The bending portion is remotely manipulated to be bent via operating wires by a manipulating member mounted on the body.
In the endoscope of the above type connectable to a television system, an image sensor (electric device) is attached to the rigid portion, and one ends of signal conductors are connected to the image sensor. A bundle of such signal conductors are passed through the bending portion, the insertion portion and the body, and are connected at the other ends to the television system outside of the body. A bundle of optical fibers for transmitting illumination light, a guide tube for guiding a forceps, and etc., are also passed through the insertion portion and the bending portion.
In the above endoscope of the type described, the bending rigidities of the signal conductors constitute one factor of the overall bending resistance offered by the bending portion when the bending portion is bent. Since the signal conductors are provided in the form of a bundle, they have contributed to an increased bending resistance of the bending portion.
When the bending portion of the above endoscope is bent in a certain direction, the bundle of signal conductors are disposed inwardly of the longitudinal axis (center line) of the bending portion. In this case, the bundle of signal conductors are required to become shorter than when the bending portion is straight Actually, however, the signal conductor bundle is not changed in length, and therefore is subjected to a compressive force, so that the bundle tends to bulge outwardly of the longitudinal axis of the bending portion. On the other hand, the elongated component parts (e.g., the above guide tube) disposed outwardly of the longitudinal axis of the bending portion is required to become longer than when the bending portion is straight. Actually, however, the guide tube is not changed in length, and therefore is subjected to tension, so that the guide tube is displaced inwardly of the longitudinal axis of the bending portion. As a result, the signal conductor bundle and the guide tube are brought into contact with each other, and interfere with each other, thus offering a resistance to the displacement or movement of each of the bundle and the guide tube. This increases the bending resistance of the bending portion.
When the bending portion is bent in a direction opposite to the above-mentioned direction, the signal conductor bundle is subjected to tension and is displaced inwardly of the longitudinal axis of the bending portion whereas the guide tube is subjected to a compressive force and tends to bulge outwardly of the longitudinal axis of the bending portion. As a result, they interfere with each other as in the above case, thus increasing the bending resistance of the bending portion.
When the bending of the bending portion continues with the signal conductor bundle and the guide tube held against each other, part of each of the two is displaced in a direction perpendicular to the direction of bending of the bending portion, and in some cases the bundle and the guide tube are disposed in respective positions which are reverse to those at the time when the bending portion is straight. In this case, however, the bending portion is twisted while being bent, and fails to be bent in a desired direction.
Further, when the signal conductor bundle and the guide tube are held in contact with each other, an axial force (i.e., tension or a compressive force) acts on the signal conductors, and this force is transmitted to the joint between the image sensor and each signal conductor which joint is formed, for example, by soldering. As a result, there is a possibility that this joint may be damaged or broken.
There is also known an endoscope of the type in which signal conductors are not positively arranged in the form of a bundle but are merely passed straight through a bending portion and an insertion portion. With this construction, however, most of the above problems are not overcome.